Inorg. Chem. 1989, 28, 2448-2451
2448
Contribution from the Department of Chemistry, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903
Tl4Re6X1, (X = S, Se): Crystal Growth, Structure, and Properties G. Huan, M. Greaney,t P. P. Tsai, and M. Greenblatt* Received September 29, 1988
Single crystals of two new phases TI4R&2 and Tl.,Re&e12 isostructural with (Rb,K)4Re&elz were synthesized by high-temperature reaction of TlX, Re, and X (X = S, Se). The structure of the selenide was solved by single-crystal X-ray investigation (space group C 2 / c , R = 0.08). The structure consists of Re6Seecluster units interconnected three-dimensionally by four Se and two Se2bridges. T1&@12 is isostructural with T14Re6Se12.The cell parameters of Tl4Re6Sl2and T14Re6Se12are a = 16.653 (2) A, b = 9.574 (3) A, c = 11.816 (8) A, B = 90.62 (2)" and a = 17.177 (3) A, b = 9.846 (2) A, c = 12.195 (2) A, B = 90.71 (2)", respectively. Z = 4 for both compounds. Physical measurements show that these compounds are semiconductingand diamagnetic, which is consistent with 24 electrons per cluster unit filling the valence band. Bond-order calculations of T14Re6Selzand other related compounds indicate a Re-Re bond order of 1 in all of the known Re6XBcluster compounds.
Introduction One of the most interesting aspects of Re3+ (d4) chemistry is that Re atoms tend to form octahedral clusters either in the form of chalcohalides1-5or in the form of chalcogenides.612 In the chalcogenides, Re6X8 clusters, the basic units of structure, are connected by X or X2 ( X = S, Se) bridging to form a three-dimensional network. Three types of bridging connections are found in the chalcogenides (Table I):b12 (1) single X bridging the clusters, as Se(6) in Figure 1, which is found in A4/B2[Re6X8]X6/2phases in Table I; (2) four single X and two dichalcogenide X2 units, as Se(5)Se(5') in Figure 1, in A4[Red(8]X4/2(X2)2/2compounds in Table I; (3) two X and four X2 bridging units as in A.,[Red(slX2/2(X2)4/2 in Table I. The nature of the connectivity is dependent on the size and number of the temary ions. In general, Se bridges provide more space than S bridges and X2 bridges provide more space than X bridges. Thus, as the size or the number of the ternary atoms increase, X bridging is partly replaced by X2 bridging (e.g. Li4Re6s11vs Na4Re6S12)and the selenides become more stable than sulfides (Rb4Re6Se12vs Rb4Re6S13). It seems that there is an optimal size range of the ternary cation for a particular composition, Le. for A4Re6X12when X = s, A = Na+ or K+ and when X = Se, A = K+ or Rb+. Since T1+ is slightly smaller than Rb' and it behaves as an alkali-metal cation,we expected the formation of T14Re6Se12.However, since TI+ is more polarizing than Rb+, it was possible that the sulfide analogue might also form. In this paper we report the preparation, crystal structure, and physical properties of the sulfur and selenide T14Re6X12phases. Experimental Section 1. Crystnl Growth. All the chemicals used in this study were of reagent grade or higher. Tl4Re6Sel2single crystals were prepared according to the following reaction: 4TlSe + 6Re + 8Se Tl4Re6Sel2
-
Stoichiometric TlSe, Re (99.997%, Aesar), and Se (99.9%, Aesar) were intimately mixed with about 10 wt % of T12Se, and the mixture was Torr) in a quartz tube. The mixture was sealed under vacuum (heated in a two-zone furnace (with the charge at the hot end of the quartz tube) slowly to 450 OC and kept at this temperature overnight. Then the temperature was raised to 1150 "C at a rate of 20 OC/h. After being kept at this temperature for 3-4 days, the product was sintered at 900 "C for about 1 week to 10 days and finally cooled down to room temperature in the course of 1 week. For single crystals of T1&2&, the preparation was essentially the same except that extra TIS was used (T1S:Re:S = 5:6:8) and the reaction temperature was 1050 OC. The binary compounds TIS, TlSe, and T13e were prepared from stoichiometric mixtures of the corresponding elements in evacuated (lo4 Torr) quartz tubes at 600 "C for 2 days (the purity of the T1 and S is better than 99.99%; both elements are from Aesar). 2. Elemental Adysis. The chemical composition for both compounds was found by a dc argon plasma emission spectrometer.
Table I. Three Types of Known Ternary Rhenium Chalcogenides
xi,,
LirRenSl,
0020-1669/89/1328-2448$01.50/0
-I
ref 11
-
NadRenS17
ref 6, 7
(X2)2/2 K7Rb,Rb,SI,
Table II. Crystallographic Data for T14Re6Sel chem formula T14Re6Se12 Z 17.177 (3) A a T b 9.846 (2) A x c 12.195 (2) A Pcald 90.71 (2)" P B V 2062 (2) A' transmn coeff fw 2882.24 R(FJ C 2 / c (No. 15) space group Rw(F,z)
ref 12
4 23 "C 0.71069 A 9.28 g/cm3 880.3 cm-l 0.51-0.99 0.081 0.078
3. X-ray Diffraction Data Collection. A multifaceted prismatic crystal was mounted on a glass fiber. The intensity data were collected on an Enraf-Nonius CAD4 automatic four-circle diffractometer at ambient temperature. Data collection parameters are tabulated in Table 11. Orientation matrices and unit cell parameters were obtained from 25 centered reflections. Axial photographs and systematic absences hkl (h + k = 2n + l), hOl (h + I = 2n + l), and OM) (k = 2n + 1) are consistent with the monoclinic space groups Cc (No. 9) and C 2 / c (No. 15). E statistics suggested the centrosymmetricspace group C2/c, and successful solution and refinement of the structure confirmed this choice. Intensity and orientation of three check reflections were monitored every 100 reflections. No significant decay was observed over the course of data collection. 4. Structure Solution and Refinement. The structure was solved by utilizing the SDP single-crystal structure determination package as supplied by Enraf-Nonius. The data were corrected for absorption by an emperical method ($), which employs $-scan data from high-x-angle reflections. Standard Lorentz, polarization, and anomalous dispersion corrections were applied to all reflections. The structure was determined by a combination of direct methods (MULTAN) and difference Fourier methods. All atoms were refined anisotropically. Full-matrix least-
(1) Opalovskii,A. A.; Fedorov, V. E. Lobkov, E. V.; Erenburg, B. G. Russ. J . Inorg. Chem. (Engl. Trawl.) 1971, 16, 1685. (2) Leduc, L.; Perrin, A.; Sergent, M. Acta Crystallogr. 1983, C39, 1503. ( 3 ) Leduc, L.; Perrin, A.; Sergent, M. C. R. Acad. Sci., Ser 3 1983,296, 961. (4) Leduc, L.; Perrin, A.; Sergent, M.; Le Traon, F.; Pilet, J. C.; Le Troan, A. Mater. Lett. 1988, 3, 209. ( 5 ) Leduc, L.; Padiou, A.; Perrin, A.; Sergent, M. J. Less-Common Mer. 1983, 95, 13. (6) Spangenberg, M.; Bronger, W . Angew. Chem., Int. Ed. Engl. 1978,17, 368. ( 7 ) Bronger, W . ;Spangenberg, M. J . Less-Common Met. 1980, 76, 7 3 . (8) Chen, S.;Robinson, W . R.J. Chem. SOC.,Chem. Commun. 1978,879. (9) Bronger, W.;Miusen, H. J. J . Less-Common Met. 1982, 83, 29. (10) Bronger, W.; Miessen, H. J.; Schmitz, D. J. Less-Common Mer. 1983, 95, 215.
( 1 1)
Present address: Exxon Research and Engineering Co., Annandale, NJ 08801.
..
Bronger, W.;Miessen, H. J.; Muller, P.; Neugroschel, R. J . Less-
Common Mer. 1985, 105, 303. (12) Bronger, W . ;Miessen, H. J.; Neugroschel, R.; Schmitz, D.; Spangenberg, M. 2.Anorg. Allg. Chem. 1985, 525, 41.
0 1989 American Chemical Society
Inorganic Chemistry, Vol. 28, No. 12. 1989 2449
I
Re(1')
Se(4')
w
Se(3')
Table 111. Elemental Analysis Data for TI4Re6Sel2 (X = S , Se) % TI % Re %X
calcd
found
calcd
found
calcd
found
TI4Re6sl2 35.24 Tl4Re6Se12 28.36
35.34 28.48
48.17 38.76
47.56 38.02
16.59 32.87
17.10 33.50
square refinement converged with a final R of 0.081. This high final R value is attributed to our inability to perform adequate absorption correction due to the unusually large linear absorption coefficient of 880 cm-' for this compound. 5. Resistivity Measurement. The resistivity measurement was carried out on a small piece of T14Re6Sel2 single crystal by using conventional dc four-probe technique. In the case of Tl4Re6Sl2, a sintered pellet was used. Ohmic contacts were made by attaching molten indium ultrasonically. 6. Magnetic Susceptibility Measurements. Susceptibility measurements were performed on single crystals by using a SQUID, Quantum Design magnetometer.
Results and Discussion 1. Single-Crystal Growth of TI4Re6XI2(X = S , Se). The methods described in the Experimental Section yield single crystals of both the sulfide and selenide. The crystals grow in a partially melted region of the charge. It appears that addition of the low melting (mp < 500 "C) binaries TI2Se, TlSe and TI2S, TIS, respectively, to the reaction mixture leads to partial melting of the charge, and crystals of TI4Re6XI2(X = S , Se) grow by flux mechanism. The crystals are small (- 1 X 1 X 1 mm3), silvery, cubelike polyhedra, with a shiny metallic luster. In some experiments, large crystals of TI4Re6Sel2with irregular shape were obtained. Figure 2 shows photographs of representative single crystals of Tl4Re6SI2and T14Re6Se12. Without the addition of T12Se or excess TIS to the starting materials for both the selenide and sulfide Tl4Re6X12, no single-crystal growth occurred; only small amounts of T12X and TIX (X = S, Se) were found deposited at the cooler end of the quartz tube (the temperature gradient across the tube is -50 "C), and polycrystallineT14Re,J12 and Rex2 were found in the charge zone (hot zone). Thus, excess TI2Se or TIS appears to prevent the decomposition of Tl4Re6xl2. Moreover, both T12X and TIX act as a flux, leading to partial solution of the starting materials, which is favorable for crystal growth. The elemental analysis results are listed in Table 111. 2. Structure of T14Re6fhlp The atomic coordinates of TI4Re6SeI2are shown in Table IV. The basic structural unit of T14Re6Sel2 is the Re6 octahedron inscribed within a cube of selenium atoms, as illustrated in Figure 1. The Re6Se8clusters are interconnected three dimensionally in the solid via diselenide (Se2) and selenide (Se2-) bridges. Crystallographic inversion centers are found at the body center of the rhenium octahedra as well as a t the midpoints of the diselenide bonds. The ar-
Figure 2. Single crystals of (top) TI4Re6SI2and (bottom) T14Re6Sel2. Table IV. Atomic Positional and Thermal Parameters' for T1,RerSet, with Estimated Standard Deviations in Parentheses X
0.0000 0.0000 0.6032 (2) 0.8403 (3) 0.7058 (3) 0.7900 ( I ) 0.8403 (3) 0.7440 (3) 0.6684 (4) 0.5822 (3) 0.9640 (4) 0.6434 (3)
Y 0.4130 (6) 0.7841 (5) 0.2514 (3) 0.1516 (2) 0.1779 (2) 0.3943 (2) 0.0843 (7) 0.4489 (6) 0.2753 (7) 0.1362 (6) 0.9751 (7) 0.0866 (6)
B,,
Z
0.2500 0.2500 0.9850 (2) 0.4748 (2) 0.3720 (2) 0.4193 (2) 0.6724 (5) 0.0697 (5) 0.7229 (5) 0.4775 (5) 0.9170 (5) 0.1918 (5)
A2
3.9 (1) 2.81 (9) 2.08 (5) 0.64 (4) 0.65 (4) 0.64 (4) 1.0 (1) 1.0 ( I ) 1.1 (1) 1.1 ( I ) 1.1 ( 1 ) 1.0 (1)
'Anisotropically refined atomic thermal parameters are given in the form of the isotropic equivalent displacement parameter defined as (4/3)[a2B( 1.1) + hZB(2.2) + c2lq3.3) + &(cos y)B(1,2) + ac(c0s B)B(1.3) + hc(cos a)B(2,3)]. rangement of the cluster within the unit cell is identical with that previously reported for K4Re6Se12and Rb4Re6SeI2.l2Selected bond distances and bond angles are sumarized in Table V. The rhenium octahedron is slightly flattened with a Re( 1)-Re( 1') distance of 3.708 (3) A in contrast to the Re(2)-Re(2') and Re(3)-Re(3') distances of 3.739 (3) and 3.724 (7) A, respectively. The average Re-Re distance along the edges of the octahedron is 2.630 A, which is close to the average Re-Re distances of 2.637 (3) and 2.641 (3) A found in the K and Rb analogues, respectively.12 This distance is shorter than that found in Re metal (2.75 A), implying the existence of Re-Re single bonds along the edges of the rhenium octahedra. The selenium cube is fairly regular with an average S e s e distance of 3.559 (5) A and average vertex angles of 90.2( I)". Each rhenium atom is bonded to four selenium atoms on the face of the selenium cube with an average Re-Se bond distance of 2.519 (4) A. In addition, each rhenium atom is bonded to a fifth selenium atom, which forms either a selenide or a diselenide bridge to an adjacent rhenium octahedron. The rhenium to diselenide bond distance is 2.582 whereas the rhenium to bridging selenide bond is slightly longer: 2.598 (3) A. The Se(5)-Se(5') distance of 2.414 (7) A is similar to those observed for diselenides in the K and Rb analogues: 2.406 (9) and 2.428 ( 1 3) A, respectively.12 The thallium ions are in irregular interstices within the lattice with Tl(3) in a general position and
a
2450 Inorganic Chemistry, Vol. 28, No. 12, 1989
Huan et al.
Table V. Selected Interatomic Bond Distances (A)and Bond Angles (deg) for T14Re6Se12 with Estimated Standard Deviations in
Parentheses Re(1)-Re( 1’) Re(2)-Re( 2’) Re(3)-Re(3’) Re( 1)-Re(2) Re( 1)-Re(3) Re(2)-Re(3) Re( l)-Se(l) Re( 1)-Se(2) Re( 1)-Se(3) Re( 1)-Se(4) Re(2)-Se( 2)
Re( l)-Re(2)-Re(3) Re(2)-Re(3)-Re( 1) Re(3)-Re( 1)-Re(2) Re( 1)-Re(2)-Re( 1’) Re( l)-Re(3)-Re( 1’) Re(2)-Re(3)-Re( 2’) Re( 3)-Re(2)-Re(3’) Re( 1)-Se(5)-Se(5’)
Distances 3.708 (3) Re(2)-Se(4’) 3.739 (3) Re( 1)-Se(5) 3.724 (7) Re(2)-Se(6’) 2.630 (4) Se( 1)-Se(2) 2.623 (4) Se( 1)-Se(4) 2.638 (5) Se(2)-Se(3) 2.495 (5) Se(3)-Se(4) 2.528 (7) Se( l)-Se(3’) 2.518 (2) Se(2)-Se(4’) Se(3)-Se( 1’) 2.535 (2) 2.518 (6) Se(4)-Se( 2’) 2.494 (4)
h
- 1
E
45
2.530 (4) 2.582 (2) 2.598 (3) 3.536 (6) 3.569 (5) 3.548 (6) 3.592 (5) 3.563 (4) 3.562 (6) 3.563 (4) 3.562 (5) 2.414 (7)
Temperature (K) Figure 3. Temperature variation of resistivity for T14Re6Se12 (0) and T14Re6S12
Angles 59.7 (1) Se(l)-Se(2)-Se(3) 60.0 (1) Se(2)-Se(3)-Se(4) 60.3 (1) Se(3)-Se(4)-Se(l) 89.5 (1) Se(4)-Se(l)-Se(2) 89.8 (1) Se(l)-Se(2)-Se(4’) 90.2 (2) Se(Z)-Se(3)-Se( 1’) 89.8 (2) Se(2)-Re( 2’)-Se(6’) 106.0 (1) Se(3)-Re(2’)-Se(6)
90.1 (2) 90.28 (7) 88.82 (6) 90.8 (1) 90.4 (1) 90.5 (1) 93.9 (1) 91.26 (8)
i
Table VI. Bond Order Calculation Results for Ternary Rhenium
Chalcogenides compd Li4Re6S1~ EuzRe5S11 Ba2Re6S1
I
Na4Re6S12 K4Re6S12
K2Rb2Re6S13 Rb4Re6S
13
CS4Re6S9.45Se3.55
TI4Re6Sel2 K4Re6Se12
Rb4Re6Se12 CS4Re&13
PBO/e 0.97 0.96 0.95 1.01 0.97 0.98 1.01 0.97 0.91 0.87 0.87 0.89
BO/e 0.98 0.98 0.97 1.01 0.99 0.99 1.oo
0.99 0.95 0.94 0.93 0.95
z
115
ref 11
^.I
0
10 9 7 7 12 12 12
-4
100 200 Temperature (K)
1-12 300
Figure 4. Temperature variation of the magnetic susceptibility for
Tl1,,Re6Sel2( X ) and TI4Re6Sl2( 0 ) .
this work 12 12 12
Tl(1) and Tl(2) on a special 2-fold position. The selenium coordination about T1( l ) , T1(2), and Tl(3) is six, eight, and seven, respectively. Overall, the structure of T14Re6Se12is isostructural with K4Re6Se12and Rb4Re6Selz. T14Re6S12was found to be isostructural with T14Re6Se12by single-crystal X-ray diffraction studies, with cell constants a = 16.653 (2) A, b = 9.574 (3) A, c = 11.816 (8) A, and /3 = 90.62 (2)O. N o further data collection and structure solution were carried out. 3. Bond-Order Calculation. The structure determination of T14Re6Se12shows that it is somewhat more regular than the K and R b analogues. This is also reflected in the results of bondorder calculations. In general, two formulas may be used: Pauling’s bond-order calculation (PBO) with d, = dl - 0.6 log nI3 and the Donnay and Allmann’s bond-order calculation (BO) where n is the bond order, d,, is the bond with n = (dl/d,)5,’4*’5 distance of order n, and d l is the bond distance of order 1. The value of dl can be obtained by the equation dl = 2.750 0.6 log 7/12 = 2.609 A. The calculated results for all structurally characterized ternary rhenium chalcogenides are listed in Table VI. It is clear that all BO values are very close to 1.00, indicating the existence of two-center two-electron Re-Re bonds in these Re6 clusters. Furthermore, the bond orders of sulfides are closer to 1.OO than those of selenides, from which we can conclude that the selenides have some matrix effect. Although Na4Re6S12was
+
(13) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell IJniversity Press: Ithaca, NY, 1960; pp 400, 403. (14) Allmann, R. Monatsh Chemie 1975, 106, 779. (15) Donnay, G.; Donnay, J. H. Acta Crystallogr. 1973, B29, 1417.
considered by Corbett to be matrix free on the basis of the existence of S/S2 bridges,16 in the Se analogues the large deviation of BO (and PBO) from 1.O is more likely due to overall bonding effects. Finally, one may note that the ternary elements have very little effect on bond order, implying that their function is mainly to provide electrons for charge balance. It is not clear yet why T14Re6Se12has a bond order (particularly PBO) slightly higher than those of the other analogous selenides listed above. 4. Chemistry of Tl4Re6XIz(X = s, se). Both compounds are stable with respect to air and moisture and can only be dissolved in oxidizing acids. The T1 atoms in the interstitial positions of the lattice have been found to be mobile. They can be partially removed in dilute HC1 or 12/CH3CN solution a t room temperature. The low limit of T1 is T11,8Re6Se12; further oxidation results in decomposition. T1 ions can also be replaced by other ions, including alkali-metal ions, Pb, and Cu, via ion-exchange reaction~.‘~ 5. Physical Properties. Seebeck coefficient measurements show that at room temperature T14Re6S12,T14Re6Se12, and T11,8Re6Se12 are p-type semiconductors. Figure 3 shows the temperature variation of the resistivity measured on a T14Re6Se12single crystal. As expected, the compound shows semiconducting behavior. The room-temperature Q cm, and the thermal activation energy resistivity is 0.96 X for conduction E, in the range 36-216 K is 0.012 eV. The room-temperature resistivity of Tl4R%SI2is much higher, as shown in Figure 3; the activation energy is 0.20 eV in the range 50-290 K. Figure 4 shows the temperature dependence of the magnetic susceptibility of Tl4Re6SeI,measured on single crystals. It shows diamagnetic and almost temperature-independent behavior in the range 300-25 K, and there is a tail at low temperature. The paramagnetic behavior of TlI,8Re6Se12 measured on a powder sample is shown in Figure 4 as well. F~~ in the temperature range (16) Corbett, J. D. Solid State Chem. 1981, 39, 56. (17) Huan, G.; Greany, M.; Greenblatt, M. Mater. Res. Bull. 1988, 23, 905.
2451
Inorg. Chem. 1989, 28, 2451-2455 32-292 K is 0.95, which gives S = 1.46, which is higher than the expected value of 1.1 for 2.2 holes per formula in Tl$e6Selz. The reason for this is not yet clear. The resistivity and magnetic measurement results are as expected. Each rhenium atom is five-coordinated by selenium atoms in a square-pyramidal geometry (dsp3), which leaves four d orbitals for each rhenium atom. According to molecular orbital calculations for M&8 clusters,18-20there are 24 orbitals per cluster, 12 of which are bonding and 12 are antibonding orbitals with a substantial energy gap between. In T14Re6X12, T1 and Re ions are formally in +1 and +3 oxidation states, respectively,z1while both X and Xz are in -2 formal oxidation state. There are 24 electrons per cluster unit, which completely fill the bonding states and leave the antibonding states empty. This explains the semiconducting behavior. The magnitude of the energy gap between bonding and antibonding states is determined by the nature of the bridging groups. Since Se 4p orbitals have greater overlapping ability than S 3p orbitals, it is not surprising that the resistivity and the activation energy of the sulfide are much higher than (18) Cotton, F. A.; Haas, T. E. Inorg. Chem. 1964, 3, 10. (19) Bursten, B. E.; Cotton, F. A.; Stanley, G. G. Isr. J . Chem. 1980, 19, 132. (20) Hughbanks, T. Inorg. Chem. 1986, 25, 1492. (21) Huan, G.; Greaney, M.; Greenblatt, M.; Liang, G.; Croft, M. Solid Srare Ionics, in press.
corresponding values of the S e analogue. Since all the electrons are paired, the diamagnetic behavior of T14Re6Se12 seen in Figure 4 is not unexpected. The upturn of the susceptibility at low temperature found for Tl4Re6SelZis probably due to the existence of paramagnetic impurities in the sample. In T11,8Re6Selz, holes are expected in the valence band and metallic and Pauli paramagnetic behavior would be anticipated. The source of the observed paramagnetic behavior (Figure 4) is not understood at this time. The magnetic data are consistent with the p-type behavior indicated by the room-temperature Seebeck measurement.
Acknowledgment. We are indebted to Dr. Tom Halbert of Exxon Research and Engineering Co., Annandale, N J 08801, for helping us with X-ray data collection and structure solution. This research was partially supported by the Office of Naval Research, the National Science Foundation-Solid State Program, under Grants DMR-84-04003, DMR-84-08266, DMR-87- 14072, and DMR-87-05620. Registry No. T4Re6Se12,117201-42-0;TISe, 12039-52-0;Re, 744015-5; Se, 7782-49-2; Tl'Se, 15572-25-5; T14Re6S12, 117201-37-3; TlS, 12039-09-7;TI, 7440-28-0; S, 7704-34-9. Supplementary Material Available: For Tl4Re6SeI2, Tables SI, SIII, and SIV, listing crystal and refinement data, anisotropic thermal parameters, and nonessential bond distances and angles (7 pages); Table SII, listing observed and calculated structure factors ( 5 pages). Ordering information is given on any current masthead page.
Contribution from the Department of Chemistry, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, Laboratoire de Chimie Theorique, Universite de Paris-Sud, 91405 Orsay, France, and Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204
Resistivity Anomalies of the Diphosphate Tungsten Bronze cs~-xP8w8040(x = 0-0.46) and Its Partially Substituted Phases c S x A y P 8 w 8 0 (A ~ ~ = Rb, Na) and C S P ~ W ~ - ~ M OSynthesis, ~ O ~ ~ : Physical Property Measurements, and Band Electronic Structure Calculations Enoch Wang,t Martha Greenblatt,*vt Idris El-Idrissi Rachidi,' Enric Canadell,*!* and Myung-Hwan Whangbo*+§ Received November 8, 1988 The cesium phosphate tungsten bronze CsPsWsOa exhibits a resistivity hump at 160 K and a resistivity upturn at -24 K. To understand the origin of these anomalies, we prepared cesium-deficient phases, Cs1-xPsW8040, and alkali-metal- and molybde, O measured ~, their electrical resistivitiesand magnetic num-substituted phases, CsxA,.PsWsOa( x + y > 1) and C S P ~ W ~ - ~ M Oand susceptibilities. Those results are interpreted on the basis of the tight-binding band electronic structures calculated for the W4OlS chain and the PSWsO40 lattice.
-
The phosphate tungsten bronze csP8wgo& contains w4018 chains (1) made of corner-sharing WO, octahedra.' Those chains C
2a
la 2b bronze is expected to be quasi-one-dimensional in electronic properties. Indeed, the electrical transport and magnetic properties of cSP8w& are consistent with this picture.' The resistivity versus temperature plot of c s P ~ w g o 4shows ~ the presence of two resistivity anomalies at -160 and -24 K: it is-semiconducting from -760 to 160 K, metallic between 160 and -24 K, and semiconducting below 24 K. In order to gain insight into the nature of the resistivity hump at N160 P8w804O1so this
lh 1"
are linked together by Pz07groups (2) to form octagonal channels, where Cs atoms reside. The W4OI8chains are isolated in CsRutgers University. 'Universite de Paris-Sud. 'North Carolina State University.
0020-1669/89/1328-2451$01.50/0
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N
(1) Goreaud, M.; Labbe, Ph.; Raveau, B. J . Solid State Chem. 1985, 56,
41.
(2) Wang, E.; Greenblatt, M. J . Solid State Chem. 1988, 76, 340.
0 1989 American Chemical Society
